Method and device for cleaning valves

ABSTRACT

The invention relates to a method and a device for the catalytic combustion of fuel which is metered into the exhaust manifold of an internal combustion engine by an injection valve. Preferably, an oxidation catalyst is positioned in the exhaust manifold of the internal combustion engine. The metered fuel is atomized in an exhaust gas flow by the injection valve. An end of the invention valve facing the direction of the exhaust gas flow in an exhaust pipe is continuously or intermittently heated by a heating device. Alternatively, an end of the injection valve which is thermally decoupled from the injection valve is directly heated by the exhaust gas flow.

PRIOR ART

DE 101 18 164 A1 has disclosed a fuel injection valve for fuel injection systems of internal combustion engines. The fuel injection valve has an actuator and a valve needle, which is operationally connected to the actuator and is acted on in the closing direction by a return spring, for the confirmation of a valve closure member. This cooperates with a valve seat surface embodied on a valve seat body to form a sealing seat. Downstream of the valve seat body, an injection port disk is provided; the injection port disk is embodied as arched in a domed fashion in a flow direction of the fuel.

Because of the stricter requirements of exhaust standards, particulate filters, in particular diesel particulate filters, are being used in autoignition internal combustion engines. The particulate filters hold back soot particles contained in the exhaust of an autoignition internal combustion engine and over the operating time of the autoignition internal combustion engine, these particles accumulate in the filter pockets of the diesel particulate filter. In order to regenerate particulate filters of autoignition internal combustion engines, the exhaust temperature is usually raised through steps taken with the engine. If the exhaust temperature increase required to burn away the soot particles cannot be achieved solely through steps taken with the engine, then an injector additionally provided in the exhaust line of the autoignition internal combustion engine meters fuel into the exhaust, which is catalytically combusted in an oxidizing converter. This discharges the heat required for the temperature increase. The HCI system (hydrocarbon injection) was developed for the additional introduction of fuel into the exhaust line of internal combustion engines. A good catalytic combustion of the fuel metered into the exhaust in the region of the oxidizing converter requires a fine distribution of the fuel that has been additionally metered in. The atomized spray should ideally be composed of evenly distributed small droplets. The required spray quality can be achieved by means of multiport nozzles that meter the additionally metered-in fuel into the exhaust through a plurality of individual ports. These multiport nozzles have a large number of small and extremely small openings, but fluid residues remaining in them and soot from the exhaust that accumulates in the multiport nozzle tends to collect in the individual ports over the operating duration of the multiport nozzle, gradually causing them to clog. As a result, there is a decrease in the quantity of fuel additionally metered into the exhaust and in particular, there is a drastic decrease in the fine droplet distribution within the atomized spray. This in turn significantly impairs the exhaust conditioning, thus also significantly impairing the effectiveness of the temperature increase produced by the oxidizing converter.

DISCLOSURE OF THE INVENTION

According to the embodiment proposed by the invention, a heating device is provided on an additional injector that introduces an atomized spray of finely distributed droplets of liquid fuel into the exhaust. Through a periodic activation of the heating device, it is possible to produce a regular cleansing combustion and evaporation, respectively, of soot and fuel accumulations in a multipoint nozzle, thus permitting an operation of the additional injector that is constant over the long term.

The multiport nozzle of the additional fuel injector, which is also referred to as an injection port disk, has at least one heating wire integrated into it. The heating wire, which constitutes the additional heating device, can on one hand, extend on the outside. i.e. on the side of the multiport nozzle or injection port disk oriented toward the flow conduit. In another embodiment variant, the at least one heating wire constituting the heating device can also be situated on the inside, i.e. on the side of the injection port disk or multiport nozzle oriented away from the exhaust flow and therefore inside the injector body of the injector for introducing additional fuel into the exhaust line. At regular intervals, the heating device raises the temperature of the injection port disk or multiport nozzle in direct proximity to the injection ports to a temperature greater than 600° C. so that adhering fuel residues and soot particles evaporate and burn, respectively.

In order to reduce the thermal load of the fuel injector in the exhaust line of the internal combustion engine, particularly in its inner chamber, the heating device can be insulated toward the inside by means of a thermal insulation.

After the fuel mist of an is metered in, it is also possible, for particulate filter regeneration purposes, to briefly raise the temperature of the injection port disk or multiport nozzle to a temperature of for example 400° C. in order to quickly evaporate adhering fuel residues. Furthermore, the embodiment proposed according to the invention also makes it possible to produce a long-term temperature increase in order to counteract or entirely prevent the diffuse accumulation of soot particles due to thermophoresis.

Another additional measure in the form of a thermal insulation between the injection port disk or multiport nozzle and the injector body of the injector is comprised of carrying out a thermal decoupling of the multiport nozzle or injection port disk from the injector body of the fuel injector. Whereas the valve tip in the region of the multiport nozzle or injection port disk is exposed to the hot exhaust flow, the thermal insulation of the injection port disk prevents the heat to which it is exposed from being transmitted into the interior of the injector body. Ideally, the injection port disk or multiport nozzle assumes the temperature of the exhaust on the side oriented toward the exhaust flow.

DRAWINGS

The invention will be described in greater detail below in conjunction with the drawings.

FIG. 1 is a schematic depiction of the exhaust line of an autoignition internal combustion engine in which, upstream of an oxidizing converter, a location is provided for the metering-in of additional fuel into the exhaust flow,

FIG. 2 shows a first embodiment variant of an end of an additional fuel injector oriented toward the exhaust flow,

FIG. 3 shows another embodiment variant of the end of the additional fuel injector oriented toward the exhaust flow, and

FIG. 4 shows an embodiment variant of the fuel injector that introduces additional fuel into the exhaust flow, equipped with thermal insulation.

EMBODIMENT VARIANTS

FIG. 1 is a schematic depiction of the exhaust line of an autoignition internal combustion engine; the exhaust line contains an oxidizing converter that is preceded by a location for the metering-in of additional exhaust.

In the exhaust line 10 of the autoignition internal combustion engine, an exhaust pipe 12 extends, via which the exhaust of the autoignition internal combustion engine flows to an oxidizing converter 18. The exhaust pipe 12 is delimited by a pipe wall 20. An inflow end of the exhaust pipe 12 is labeled with the reference numeral 14 and an outflow end of the exhaust flow is labeled with the reference numeral 16. The outflow end 16 of the exhaust pipe 12 constitutes the inflow end of the oxidizing converter 18. The exhaust pipe 12 is embodied as symmetrical to its axis of symmetry 22.

An injection valve 24 is integrated into the pipe wall 20 of the exhaust pipe 12. The injection valve 24 is connected via a supply line 25 for example to the fuel tank of the vehicle equipped with the autoignition internal combustion engine and is supplied with fuel via this line.

The injection valve 24 has a valve body 26 that passes through the pipe wall 20 of the exhaust pipe 12 and protrudes partway into the exhaust flow passing through the exhaust pipe 12. Inside the valve body 26, there is a valve piston 28, which is only shown schematically here and which is able to move in the vertical direction indicated by the double arrow provided in FIG. 1. The valve piston 28 cooperates with a valve seat 30 embodied in the valve body 26. Below the valve seat 30 in the valve body 26 of the injection valve 24 is a cavity labeled with the reference numeral 36, which is delimited by the valve seat 30 and by an injection port disk 32.

By means of the injection port disk 32, in which multitude of extremely small openings are provided for producing a finely distributed atomized spray, additional fuel, indicated by the reference numerals 34, is introduced into the exhaust flow posing the exhaust pipe 12. The smaller the droplet distribution is in the atomized spray produced by the injection port disk 32, the better the mixture of the additional fuel with the exhaust flow is and therefore the more uniform the combustion that can be achieved in the oxidizing converter 18.

FIG. 2 shows a section through the end of the injection valve shown in FIG. 1 that is oriented toward the exhaust flow.

FIG. 2 shows that the vertically movable valve piston 28 is situated inside the valve body 26 of the injection valve 24 and cooperates with a valve seat 30 likewise embodied inside the valve body 26. On the valve seat 30, an opening is provided, which can, for example, be embodied as circular and can be closed by the end of the valve piston 28 oriented toward the valve seat 30. Depending on the stroke travel of the valve piston 28, the opening in the valve seat 30 is completely or partially opened so that additional fuel flows out from the inside of the valve body 26, via the open valve seat 30, and to the cavity 36.

The valve body 26 is delimited by an injection port disk 32 that is preferably joined in an integral fashion to the valve body 26 at joining points 54. The injection port disk 32 preferably has a multitude of individual openings 48. The joining points 54 between the valve body 26 and the injection port disk 32 can, for example, be embodied in the form of welding seams; it is alternatively also possible for the injection port disk 32 to be screwed into the valve body 26 or for the valve body 26 to be embodied in the form of a one-piece component with an integrated injection port disk 32.

FIG. 2 shows that a heating device—embodied here in the form of a heating wire 44—is associated with the outside of the injection port disk 32, i.e. the side of the injection port disk 32 oriented toward the exhaust flow in the depiction in FIG. 1. A spacing that corresponds to the distance between individual heating wires 44 of the heating device is labeled with the reference numeral 56 in the depiction in FIG. 2. The at least one heating wire 44 of the heating device preferably extends so that the at least one heating wire 44 extends over the solid material of the injection port disk 32 and does not cover the openings 48 embodied in the injection port disk 32. Activation of the heating device, constituted by the heating wires 44 shown in FIG. 2, produces a heating of the injection port disk 32 so that fuel remaining in the injection openings 48 evaporates and soot particles that have accumulated on the injection port disk 32 in the vicinity of the individual openings 48 are burned away. The first embodiment variant of the heating device shown in FIG. 2 provides long-lasting assurance of the quality of the atomized spray of additional fuel produced by the injection valve 24 because the geometry of the individual openings 48 in the injection port disk 32 is not impaired by fuel residues or soot particles that clog the individual openings 48. The thickness of the injection port disk 32 is labeled with the reference numeral 46. The cavity 36 in the injection valve 24 is defined by a first end surface 38 of the injection port disk 32, an inner wall 42 of the valve body 26, and the valve seat 30 with the opening provided in it. In the embodiment variant shown in FIG. 2, the heating device is situated on a second end surface 40 of the injection port disk 32, i.e. on its surface oriented toward the exhaust flow.

FIG. 3 shows another embodiment variant of the outflow end of an injection valve that meters additional fuel into the exhaust flow.

By contrast with the first embodiment variant of the injection valve 24 shown in FIG. 2, the heating device, including at least one heating wire 44, is situated on the inside of the injection port disk 32, in this case, on the first end surface 38 inside the cavity 36 in the valve body 26. According to the embodiment variant of the heating device of the injection valve 24 shown in FIG. 3, the at least one heating wire 44 extends along the first end surface 38 of the injection port disk 32 arranged in a spacing 56. In the embodiment variant shown in FIG. 3, the provision of an inner heating device, i.e. one situated inside the cavity 36 of the valve body 26 and including at least one heating wire 44, achieves the fact that the heating device itself is not contaminated by soot particles contained in the exhaust flow of the autoignition internal combustion engine. The spacing 56—with which the at least one heating wire covers the first end surface 38 of the injection port disk 32, for example in a meandering fashion—results in an open flow cross-section to the individual openings 48 embodied in the injection port disk 32.

When the at least one heating wire 44 of the heating device situated against the injection port disk 32 is supplied with current until it reaches a temperature T_(max) of approximately 600° C., the fuel remaining in the individual openings 48 evaporates and particles, e.g. soot particles, situated in the individual openings 48 of the injection port disk 32 are burned away. The cross-section through which the additional fuel is injected into the exhaust flow is therefore retained. Furthermore, the injection port geometry remains unaltered over the operating time of the injection valve 24 so that there is no adverse effect on the region in which the atomized spray is introduced into the exhaust flow.

Also in the second embodiment variant shown in FIG. 3 of the injection valve 24 shown in FIG. 1, the valve seat 30 is embodied inside the valve body 26 and its opening can be either completely opened, completely closed, or partially opened by the valve piston 28 as a function of its vertical stroke. According to the second embodiment variant of the injection valve 24 shown in FIG. 3, the injection port disk 32 can be either integrally joined to the valve body 26 at the joining points 54 or can be fitted into it in a nonpositive, fictionally engaging fashion, e.g. be shrink-fitted into it.

FIG. 4 shows another embodiment variant of the injection valve 24 that is depicted only in schematic form in FIG. 1.

FIG. 4 shows that a thermal insulation 50 is accommodated in the cavity 36 between the valve seat 30 and the injection port disk 32. The thermal insulation 50 separates the injection port disk 32 situated at the exhaust flow end from the inside of the valve body 26. The thermal insulation 50 includes individual openings 52 that are embodied with a spacing 58 so that the openings 52 of the thermal insulation 50 are aligned with the individual openings 48 in the injection port disk 32. This permits an unhindered flow of the additional fuel stored in the valve body 26 to the injection port disk 32 when the valve seat 30 is open. In the embodiment variant according to FIG. 4, the heating device that is constituted by the at least one heating wire 44 is eliminated.

The embodiment variants of the heating device shown in FIGS. 2 and 3, which is represented by the at least one heating wire 44, can be supplied with current at regular intervals so that the temperature of the injection port disk 32 in direct proximity to the individual openings 48 rises to a temperature level of greater than 600° C. At this temperature, fuel residues that hinder the emerging flow of fuel in the individual openings 48 evaporate. In addition, soot particles that have accumulated in the flow cross-sections of the individual openings 48 burn away at this temperature level. If the heating device composed of the at least one heating wire 44 is situated resting against the first end surface 38 as shown in FIG. 3 or against the second end surface 40 as shown in FIG. 2, it is then possible, although this is not shown in FIGS. 2 and 3, for a thermal insulation 50 to be accommodated in the cavity 36 of the valve body 26, as in the exemplary embodiment show in FIG. 4.

In addition to a uniform tempering of the injection port disk 32 through a constant supply of current to the heating device, which includes at least one heating wire 44, it is also possible, shortly after the metering-in of fuel for particulate filter regeneration, to increase the temperature of the injection port disk 32 to a temperature level of approximately 400° C., for example, in order to rapidly evaporate fuel residues adhering in the individual openings 48. In addition, it is also conceivable for there to be a longer-lasting temperature increase in order to counteract the diffuse accumulation of soot particles by thermophoresis and in the ideal case, to prevent this entirely.

The exemplary embodiment shown in FIG. 4, in order to increase the temperature of the injection port disk 32, a heating device, for example including at least one heating wire 44, can also be completely eliminated if the temperature increase of the injection port disk 32 is produced entirely by the exhaust flow passing through the exhaust pipe 12. In this case, the thermal insulation 50 decouples the inside of the valve body 26 of the injection valve 24 from the injection port disk 32. Preferably, the thermal insulation 50 is accommodated in the cavity 36 in the valve body 26, which cavity is delimited by the valve seat 30 on the one hand and by the injection port disk 32 on the other. Since the injection port disk 32 is exposed to the hot exhaust flow and is therefore heated very powerfully, the thermal insulation 50 situated in the cavity 36 prevents the temperature level of the injection port disk 32 from acting on the valve body 26 of the injection valve 24. In addition, because of the thermal insulation 50, the heating action of the exhaust flow on the injection port disk 32 remains limited and after a corresponding heating time, the injection port disk 32 also actually assumes the temperature of the exhaust flow. In an embodiment variant not shown in the drawings, the thermal insulation 50 can also be accommodated on the side of the injection port disk 32 oriented toward the exhaust flow. In this case, the thermal insulation 50 can be embodied by means of a coating composed of a thermal ceramic thin layer, it being necessary to assure that this layer has as little influence as possible on the exhaust flow inside the exhaust pipe 12. The thermal insulation 50 embodied in the form of a coating composed of a thermal ceramic thin layer is applied to the injection port disk 32 so that the injection openings 48 provided in it are not covered by the thermal ceramic thin layer. 

1-10. (canceled)
 11. A method for catalytic combustion of fuel, which fuel an injection valve has metered into an exhaust line of an internal combustion engine, through the use of an oxidizing converter, comprising the steps of: a) the injection valve atomizing the metered-in fuel in an exhaust flow; and b₁) a heating device continuously or periodically heating an end of the injection valve oriented toward the exhaust flow in an exhaust pipe; or b₂) heating an end of the injection valve that is thermally decoupled from the injection valve directly by the exhaust flow.
 12. The method as reciting claim 11, wherein the metered-in fuel is atomized by means of an injection port disk accommodated at the end of the injection valve oriented toward the exhaust flow.
 13. The method as reciting claim 11, wherein in step b₁), the end of the injection valve oriented toward the exhaust flow is heated at regular intervals to a temperature level of approximately 600° C. or is heated to a temperature level of approximately 400° C. after additional fuel has been metered-in.
 14. The method as reciting claim 11, wherein in step b₂), the thermal decoupling of the end of the injection valve is achieved by means of a thermal insulation.
 15. A device for catalytic combustion of fuel, which fuel an injection valve has metered into an exhaust line of an internal combustion engine, comprising: an injection port disk equipped with a plurality of individual openings being situated at an end of the injection valve oriented toward exhaust flow in the exhaust line, the injection port disk being associated with a heating device, which heating device includes at least one heating wire, or the injection port disk being thermally decoupled from a valve body of the injection valve by means of a thermal insulation.
 16. The device as recited in claim 15, wherein the at least one heating wire extends along one of two surfaces of the injection port disk.
 17. The device as recited in claim 16, wherein the at least one heating wire is accommodated inside a cavity of the injection valve and is thermally insulated from the valve body of the injection valve.
 18. The device as recited in claim 16, wherein the at least one heating wire extends in a meandering fashion on one of the surfaces of the injection port disk.
 19. The device as recited in claim 15, wherein the thermal insulation is situated in a cavity above the injection port disk in the valve body.
 20. The device as recited in claim 16, wherein individual coils of the at least one heating wire extend with a spacing, which permits passage of fuel through individual openings of the injection port disk, or through openings of the thermal insulation are aligned with individual openings of the injection port disk.
 21. The device as recited in claim 19, wherein individual coils of the at least one heating wire extend with a spacing, which permits passage of fuel through individual openings of the injection port disk, or through openings of the thermal insulation are aligned with individual openings of the injection port disk. 